The invention relates generally to laminated plastic structures used in recreational products, and more particularly to bodyboards for riding on waves in ocean surf.
Bodyboards and other amusement and recreational devices made of flotation foam are often covered with outer skin surface made of plastic or another type of non-foam sheet material to help reduce drag. On bodyboards, a non-foam skin surface is usually applied to the bottom of the board. Various techniques are employed to fabricate and adhere an outer skin to the foam core of bodyboards. One prior art technique is found in U.S. Pat. No. 4,850,913, which discloses a process for heat-laminating a film layer to a thin sheet of foam which is then bonded to the foam core of the board.
One limitation of prior art systems for adhering a film skin to the foam core of a bodyboard is the difficulty or impossibility of creating durable graphic images on the skin. For example, the '913 patent discloses how patterns of color can be applied between the outer film layer and the underlying foam during the heat-lamination process. Color concentrate is added to the surface of the film to produce elongated patterns of stripes or waves, but the result is almost certainly indistinct color variations and patterns, not sharp graphics. The '913 patent also proposes the use of a Mylar (trademark) transfer pattern for applying a logo to the outer skin, but such an image transfer process produces impermanent graphics subject to scratching and wear.
It would be advantageous to provide a system for applying sharp, distinct and wear-resistant graphics to semi-rigid foam substrates. Such a system would permit the production of bodyboards and other amusement devices decorated with bold, durable graphic patterns.
It would also be advantageous to provide a foam-core bodyboard for use in ocean surf which has a slick nonfoam bottom surface imprinted with distinct, reproducible graphics.
Accordingly, the present invention provides a bodyboard for supporting a rider during travel in ocean surf. The bodyboard comprises an elongate plank made of semi-rigid foam having a thickness generally in the range of 1-inch to 4-inches. An expanse of skin is bonded to the foam at selected locations, surrounding and enclosing the foam core of the board. The skin includes a plurality of layers bonded adhesively together, including an outer layer of nonopaque polyolefin film material, such as extruded polyethylene, and an inner layer of polyolefin film. The thickness of the nonopaque outer layer is generally in the range of 1-mil to 5-mils. The outer layer of nonopaque polyolefin film includes graphical images formed on the side of the film which faces the core, whereby the images are visible through the outer layer to decorate the bodyboard.
The invention further provides a method of applying printed graphics to semi-rigid foam substrates of the type having a thickness generally exceeding 1-inch. The first step in the method is to provide a skin for application to the foam substrate. The skin is formed by the following steps: Graphics are imprinted on one side of a nonopaque (i.e., clear) thin-film plastic sheet having a thickness generally in the range of 2-mils to 5-mils. The graphics are imprinted in a reverse pattern, for viewing through the nonopaque sheet. After the imprinting step, the nonopaque sheet is adhesively bonded to a second thin-film plastic sheet with the graphics-imprinted side of the nonopaque sheet facing the second sheet. The second sheet is preferably opaque, resulting in a layered skin with the imprinted graphics visible through the nonopaque sheet. The preferred thickness of the second (opaque) thin-film plastic backing sheet is generally in the range of 2-mils to 5-mils, resulting in a graphics-imprinted, laminated skin with an overall thickness generally in the range of 4-mils to 10-mils.
After producing the skin, the skin is bonded to the foam substrate by heating a skin-receiving surface on the foam to a temperature generally in the range of 180.degree. Fahrenheit to 220.degree. Fahrenheit. Finally, the skin, with the nonopaque sheet oriented outwardly, is pressed against the heated skin-receiving surface to adhere the skin to the foam, whereby a skin covering with visible graphics is provided on the foam.
The above-described process is preferably carried out on a conveyor which transports the foam substrate through a heating zone which heats the skin-receiving surface to the specified temperature. The skin, previously fabricated and collected on a roll, is conveyed by one or more rollers to the skin-receiving surface of the foam, where the skin and foam are pressed together between nip rollers which apply a compressive force generally in the range of 10 pounds per-square-inch to 30 pounds per-square-inch to adhere the skin to the foam.